The Brisbane Tuff (226 Million Years)
Ad Astra’s new creative complex at 210 Petrie Terrace in Brisbane City includes two new theatres – Galaxy, a 151-seat theatre, and Pluto, a 44-seat black box space. During renovations to Pluto, an original foundation stone was uncovered beneath floor level, revealing an early piece of Brisbane’s history – a dramatic day in Brisbane’s history more than 226 million years ago! Curious to find out more, we asked theatre lighting designer extraordinaire and Ad Astra creative, David Walters, who also happens to be a qualified geologist! David told us that the Tuff was deposited by a violent volcanic eruption and records Brisbane’s paleolandscape on one very dramatic day.
“The foundation stone in the new Pluto space is Brisbane Tuff, one of the first building stones used in Brisbane. You can see it today in the city’s structures from curb stones to cathedrals. It is also seen in its natural form at locations such as Kangaroo Point Cliffs. The ancient stone predates all human history and was created from an explosive geological event around the time of Queensland’s very early dinosaurs.
“Brisbane Tuff is also called Ignimbrite. In Latin that means ‘fiery shower’. As the name suggests, there would have been a violent eruption, and fiery skies with ash clouds, dust particles and super-heated gases spewing into the air to form huge rolling semi-liquid clouds. The temperature would have been around 1000 degrees Celsius – super heat and an enormous force, with these ash clouds hurtling down valleys at up to 200km an hour. The rock that formed once the ash cooled preserves a dramatic moment in time, and it’s a fascinating glimpse into Brisbane’s pre-history.
“Brisbane Tuff has had a huge impact on Brisbane – it’s the bedrock on which central Brisbane lies. It has influenced the course of the river and has seriously shaped the Brisbane we know today. Brisbane Tuff has been integral to the construction of Brisbane from the earliest days – it was recognised immediately as a fabulous building stone. So, today you can see it all the way from Chermside down to Tarragindi in remnant quarries such as the cliffs in Windsor, the city council depot in Kedron, the Royal Brisbane Hospital carpark, and the Howard Smith Wharves under the Story Bridge. Convict constructions like the Commissariat Stores in William St and the Spring Hill Windmill survive thanks to the longevity of Brisbane tuff and the Cathedral of St Stephen and St Mary’s Anglican Church showcase this remarkable building stone. You see the signs around Kangaroo Point Cliffs – “Beware falling rocks” – that’s the Brisbane Tuff!”
“Within the rock wall in Ad Astra’s Pluto black box theatre space, there’s a block of the Tuff that has pebbles in it. This suggests it might have taken from the bottom of the Tuff formation where the ash cloud settled on the alluvium derived from the existing country rock – the main rock formation around Brisbane – which formed over 300 million years ago. And while the Tuff was just too hot to preserve any fossils beyond charred plant remains, it certainly captures an astonishing geological story, and a day in drama for Brisbane.”
